Report2

2010

Industrial Attachment Report

Submitted by: Tham Jia Yin, Sarah

Supervised by: Mr. Eric Tan (SAESL)

Professor Zhou Wei (NTU)


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Abstract:

As part of her Aerospace Engineering undergraduate studies, the author served as an

intern at Singapore Aero Engines Services Limited (SAESL) from the 11th of January to

the 11th of June 2010. The author was attached to the department of repair development.

Being a Rolls-Royce jet engine Maintenance, Repair and Overhaul (MRO) workshop,

the role of the aforementioned department was to increase and improve the repair

capabilities of the company through the introducing and assimilating of new

technologies into the company’s daily functions.

This report documents the author’s 22 weeks spent as a trainee engineer under the

guidance of her supervisor and mentors. The report first presents the corporate profile of

SAESL as Rolls Royce’s Centre of Excellence, before introducing the working

principles and different sections of a commercial jet engine. Following that, the report

chronicles the major projects undertaken by the author during her period of employment,

the most significant being the assisting in the setting up of a new repair cell, the Front

Combustion Liner cell.

Through the various tasks, the author was exposed to the many levels of work that take

place in such an engineering company, from the menial, to the mundane, to the formal.

After her 5-month stint in SAESL, the author has had her technical knowledge solidly

reinforced, and has drastically widened her perspective on the industry. Now equipped

with a wealth of new hands-on experience and workplace skills, the author is much

better prepared for the working life that lies ahead.


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Acknowledgements:

The author would like to extend her sincerest gratitude to the following personnel for

their invaluable assistance and guidance rendered throughout her attachment:

• Mr Chan Swee Heng, Manager, Engineering Department

• Mr Eric Tan, Head, Repair Development, and supervisor to the author

• Mr Koh Li Teck, Principal Technologist

• Mr Adrian Chia, Engineer, Repair Development, and mentor to the author

• Mr Alex Ong, Engineer, Repair Development

• Miss Khoo Yi Wen, Engineer, Engineering Department

• Mr Chua Koon Tiong, Inspector, Machining Cell

• All technicians in the various repair cells at SAESL

The author would also like to thank all her colleagues, of whom there are too many to

name, for their tolerance shown toward her inexperience, and their guidance in her

everyday tasks. Special thanks also go out to SAESL for the wonderful opportunity

presented to the author to pursue her Industrial Attachment at such an established

company placed at the forefront of the MRO industry. Last but not least, the author

would like to thank her tutor, Dr. Zhou Wei, and the NTU Career and Attachment

Office, for making such a life changing experience available for her.


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Table of Contents

1. Introduction to Industrial attachment................................................................................... 1

1.1. Objective: ....................................................................................................................... 1

1.2. Scope: ............................................................................................................................ 2

1.3. Company Profile ............................................................................................................ 3

1.4. Repair Development Department ................................................................................. 5

2. The Jet Engine ........................................................................................................................ 6

2.1. Fan ................................................................................................................................. 6

2.2. Compressor .................................................................................................................... 7

2.3. Combustor ..................................................................................................................... 8

2.4. Turbine ........................................................................................................................... 9

3. Orientation – Induction to the shop floor ........................................................................... 11

3.1. Fan blade cell ............................................................................................................... 11

3.2. Fitting cell .................................................................................................................... 13

3.3. Shot peening cell ......................................................................................................... 15

3.4. Machining .................................................................................................................... 17

4. Repair scheme reviews ........................................................................................................ 20

4.1. Standard Equipment .................................................................................................... 21

4.2. Consumable Materials ................................................................................................. 22

4.3. Equipment capabilities ................................................................................................ 22

5. The Front Combustion Liner cell .......................................................................................... 25

5.1. The Front Combustion Liner ........................................................................................ 25

5.2. GOM machine – Optical measuring technique ........................................................... 27

5.3. DMG – Automated Machining ..................................................................................... 29

5.4. Planning the repair matrix ........................................................................................... 31


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6. Personal Reflections and Conclusion ................................................................................... 33

6.1. Personal Reflections .................................................................................................... 33

6.2. Conclusion ................................................................................................................... 36

References

Appendix A – Organizational Chart of SAESL

Appendix B – Full Repair Scheme K004

Appendix C – Repair Capability Form

Appendix D – SolidWorks Model of the Trent 500 Front Combustion Liner

Appendix E – Scheme Matrix for the Front Combustion Liner Cell


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Table of Figures

Figure 1 – Birds-eye view of the SAESL facility .............................................................................. 3

Figure 2 – SAESL’s in-line engine gantry (left) and cleaning line (right) ....................................... 4

Figure 3 – Cutaway of a classic jet engine ..................................................................................... 6

Figure 4 – Cutaway of a jet engine compressor ............................................................................ 7

Figure 5 – A jet engine combustion chamber ............................................................................... 8

Figure 6 - pictorial of airflow in a jet engine turbine ..................................................................... 9

Figure 7 – Workflow of a typical fan blade repair ....................................................................... 12

Figure 8 – Different surfaces of the fan blade after various processes ...................................... 13

Figure 9 – the workflow for the repair of a composite fairing .................................................... 14

Figure 10 – fundamentals of shot-peening ................................................................................. 15

Figure 11– Types of machining: a) Turning; b) Milling; c) Drilling; d) Grinding ........................... 18

Figure 12 - Clocking the reference datum before drilling ........................................................... 19

Figure 13 – Flowchart for the scheme review database ............................................................. 20

Figure 14 – The combustion rear inner case ............................................................................... 21

Figure 15 – Flowchart of the scheme review process ................................................................. 23

Figure 16 – Cross section of a combustion chamber ................................................................... 25

Figure 17 – Close-up of the FCL: a) Cooling holes b) Liner tiles ................................................... 26

Figure 18 – The GOM scanning unit and the triangulation principle .......................................... 27

Figure 19 – The Front Combustion Liner in scan (left) and in 3-D model (right) ......................... 28

Figure 20 – Inspection data of the FCL ........................................................................................ 28

Figure 21 – The probe of the adaptive machine ......................................................................... 29

Figure 22 – Probing an uneven surface before machining .......................................................... 30

Figure 23 – A sample repair matrix ............................................................................................. 31

Chapter One – Introduction to Industrial Attachment

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1. Introduction to Industrial attachment

1.1. Objective: As part of the curriculum for students pursuing a degree in Aerospace Engineering at

Nanyang Technological University, Industrial Attachment is a compulsory 22-week

programme conducted for students in a relevant engineering company. The objective of

this attachment is to reinforce the university’s technical and theoretical teachings by

providing an opportunity for the students to apply it on valuable hands-on opportunities,

preparing them for their professional future as engineers.

The attachment program should enable the students to:

• Apply their technical knowledge

• Gain hands-on experience

• Acquire the necessary skills all good engineers should be equipped

with, such as manpower management, attention to detail, creativity and

flexibility in application of technical know-how, etc.

• Strengthen their work integrity and values through their time spent in a

professional capacity at the company and

• Pick up vital inter-personal skills that will help to the student build a

cohesive working environment for him/her with his/her colleagues.


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1.2. Scope: The scope of this Industrial Attachment was for the author to fully assume the role of a

Development Engineer. A Development Engineer oversees the repair capabilities of

SAESL, and is in charge of introducing and setting up new technologies that will

expand and improve the company’s present capabilities.

During her attachment, the author was required to familiarize herself with the various

repair operations being carried out in SAESL. Having done so, she was then put in

charge of SAESL’s scheme review process. This process entailed reviewing the various

repair schemes provided by Rolls-Royce, and then deciding and declaring if it was

within SAESL’s capacity to carry out the respective repairs. Knowledge of the shop

floor was essential for this task, as the author needed to know exactly which types of

repairs could be carried out, and which types could not and hence needed to be

outsourced.

The bulk of the author’s time at SAESL was dedicated to her largest project, the setting

up of the new Front Combustion Liner (FCL) cell. Incorporating cutting edge

technologies like optical measuring scans and adaptive machining, this cell will serve a

niche market around the world for FCLs. The cell was developed from scratch;

machines had to be imported, its software had to be set up, and all the necessary

paperwork from Rolls-Royce had to be processed.

This report will document these tasks undertaken by the author during her employment

in SAESL.


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1.3. Company Profile Singapore Aero Engine Services Private Limited (SAESL) was established in 1999 as a

S$185 million tripartite joint venture between SIA Engineering Company (50%), Rolls-

Royce (30%) and Hong Kong Aero Engine Services Limited HAESL (20%). It is part

of Rolls-Royce’s Aero Repair and Overhaul Committee (AROC) network of Rolls

Royce engine Maintenance, Repair and Overhaul (MRO) repair facilities around the

world. As part of AROC’s network, SAESL operates as the MRO centre of Rolls-Royce

Trent engines within the Far East, the Middle East, Australasia and the Pacific Rim.

Figure 1 – Birds-eye view of the SAESL facility[1]

SAESL is a Rolls-Royce authorized MRO shop, and is the only shop in the world

capable of servicing the complete line of Trent Family engines as listed below:

• Trent 500 Series Engines




SAESL is also the first MRO facility in the world to service the new Trent 900 engine

that powers the famous Airbus A380.


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Covering an expanse of 30,000 square metres, SAESL's facility is designed to repair up

to 250 Trent engines a year. The building houses state-of-the-art aero engine MRO

systems, including the in-line gantry system for engine strip and assembly, as well as

the world’s first fully automated chemical cleaning line.

Figure 2 – SAESL’s in-line engine gantry (left) and cleaning line (right) [1]

In 2007, SAESL’s Compressor Blade Cell was awarded the coveted Rolls-Royce Centre

of Excellence – Gold award. This $13 million repair facility was the first in the world to

employ robots as part of their processes, and the employment of such a technology

helped to reduce required man-hours, lower repair costs, and hasten the cycle time for

each repair.

Presently, SAESL’s clientele includes Singapore Airlines, Virgin Atlantic Airlines,

Emirates, Thai Airways, Qatar Airways, Air New Zealand, and many more. With such a

sound customer base and a growing list of impressive accolades bearing testament to the

first-class repair services offered by SAESL, it comes as no surprise that SAESL is

known around the world as a Trent Centre of Excellence.


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1.4. Repair Development Department The repair development department in SAESL is a branch of the Engineering

department, and is responsible for introducing new technologies into SAESL’s

production line. The development engineers constantly study emerging technologies

and identify relevant ones. They then undertake the project of importing the

technologies into SAESL, and ensuring its full functionality in terms of hardware,

software, and skilled manpower. This department is vital in ensuring that SAESL

remains at the forefront of the MRO industry with the employment of cutting edge

technology, and provided an excellent learning ground for the author.

Chapter Two – The Jet Engine

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2. The Jet Engine

Figure 3 – Cutaway of a classic jet engine [2]

The figure above shows a cutaway of a classic jet engine. Comprising a fan, a

compressor, a combustor, a turbine and an exhaust nozzle, it relies mainly on Newton’s

Third Law of motion to deliver the thrust required to power a plane. In the subsequent

paragraphs, the mechanics of a jet engine will be detailed according to its individual

modules.

2.1. Fan The fan is the primary producer of thrust in a jet engine. Functioning as a low pressure

compressor, the air that passes through the fan is compressed to almost twice its original

pressure. Approximately 10 to 20% of the compressed air then enters the engine core.

The remaining 80% of the air is immediately expanded through the constricted exhaust

of the fan case. The expanded air accelerates, and it is this accelerated air that, in


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accordance with Newton’s Third Law of reactive forces, provides the engine with

approximately 75% of its overall thrust delivered [2].

2.2. Compressor

Figure 4 – Cutaway of a jet engine compressor[2]

A single stage compressor is made up of an adjacent row of rotor and stator blades. The

rotor blades are mounted onto a bearing drum connected via a shaft to the turbine at the

rear of the engine which rotates the rotor at a high speed. When the air passes through

the rotor, some kinetic energy from the rotor is transferred to the air, causing a pressure

rise. The stator located downstream (seen as Variable Stator Vanes (VSVs) above), then

removes the swirl in the air caused by the rotating motion of the rotor, preparing it for

the next stage of the compressor.

The fan, as mentioned, functions as a low pressure compressor (LPC), which is

followed by the Intermediate Pressure Compressor (IPC). The figure above shows

labels such as IP1 and IP8. IP1 stands for Intermediate Pressure Compressor Stage 1

and IP8 for stage 8. Several stages are required in a compressor, as a single stage is not

able to accomplish the necessary pressure rise. However, it is important to note that the

rotors are connected to a single bearing, and hence rotate at the same speed.


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The final module of the compressor is known as the High Pressure Compressor (HPC).

The HPC operates at a higher rotational speed than the IPC due to the decreased

compressibility of the pressurized air, hence the need for higher energy transfers. By

separating the HPC from the IPC, the two modules are connected to different sections of

the turbine that will allow the two compressors to rotate at different speeds. This split

compressor technology is a Rolls-Royce trademark, and is one of the major contributing

factors for the superior efficiency of Rolls-Royce’s Trent engines.

2.3. Combustor

Figure 5 – A jet engine combustion chamber[2]

The combustor handles the task of burning the large volumes of compressed air exiting

the compressor. The air exiting the compressor is drastically decelerated, and enters the

main component of the combustion chamber, the Front Combustion Liner (FCL). A fuel

injector sprays fuel into the incoming air, creating a highly combustible air/fuel mix. A

spark plug then ignites the mixture that will burn in a self-subsisting flame for the entire

flight cycle. The combustion process dramatically raises the temperature of the


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incoming air. According to the laws of thermodynamics, the pressure drop in the hot air

as it expands through and turns the turbine is less than its initial pressure rise caused by

the compressor. The excess pressure then becomes available as engine thrust when it is

exhausted from the nozzle.

2.4. Turbine

Figure 6 - pictorial of airflow in a jet engine turbine[2]

Like the compressor, the turbine is made up of rows of stators and rotors. However, in

the turbine, the stator is placed before the rotor. Following the combustion process, the

high temperature-and-pressure gas is forced into the High Pressure Turbine (HPT). The

nozzle guide vanes swirl the air in the direction of the turbine blades’ rotation. Energy is

then extracted from the tailored flow that creates a torque on the turbine, causing the

turbine disc to rotate, and in turn drive the compressor at the front of the engine.

After passing through the entire core of the engine, the air is exhausted to the

atmosphere in a constricted exhaust, just like that of the fan. The exhaust, being a high

velocity and high pressure gas stream, acts as a reactive force on the rear of the engine,

Turbine

Nozzle Guide Vanes (stator)


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contributing to the other 25% of the jet engine’s overall thrust. With that, this chapter

concludes the introduction to the working principles of the jet engine.

Chapter Three – Orientation on the Shop Floor

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3. Orientation – Induction to the shop floor Repair jobs come from airlines all over to world to SAESL in three forms – as a whole

engine, as individual modules (for example: a high pressure compressor), or as a single

component. The engines and modules are stripped to their individual parts before being

sent for cleaning, and subsequently, inspection. Parts found to be damaged beyond

repair are discarded, and replaced with new parts. Parts found to be damaged but still

repairable are then sent to the shop for repairs according to standard repair procedures

set out by Rolls-Royce.

In her first month at SAESL, the author was attached to various repair cells for short

periods of time. The purpose of this was to introduce the author to the different types of

repair carried out in SAESL, to prepare her for her subsequent tasks in the company.

3.1. Fan blade cell The first cell that the author was attached to was the fan blade cell (FBC). Unlike other

cells, the FBC was different in that it was a component cell. A component cell is a

stand-alone, capable of existing on its own without support from other cells. The FBC

repairs only fan blades, and is able to independently carry out most repairs that a fan

blade might require.

There are two standard repairs that all fan blades sent for overhaul will undergo.

Assuming no abnormal damages such nicks or dents on the blades, each blade will have

its leading edge profile and aerofoil surface restored during overhaul. Throughout the

author’s two-day attachment, she assisted the technicians in the cell in carrying out the

above two repairs on a set of Trent 800 engine fan blades.


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Figure 7 – Workflow of a typical fan blade repair

Each engine consists 26 fan blades. The figure above demonstrates the procedure of a

typical fan blade repair. After being stripped from the engine and cleaned, the set of

blades were sent to the FBC. The author inspected the blades visually and with

ultrasound to check for surface damage or interior cracks. None were present. The

blades then had their leading edge profile checked against a standard mould provided by

Rolls-Royce. After several cycles of engine run, the blades which were initially

designed aerodynamically for drag reduction purposes had experienced erosion of their

leading edge. The author used a hand-held grinding machine to file the leading edges of

the blades back to their original profile, and polished them with an abrasive stone to

smoothen the edge.


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Figure 8 – Different surfaces of the fan blade after various processes

Following that, the blades were loaded into the glass peening booth, for the surface of

the blade to be blasted with glass beads. Glass peening is similar to shot peening (to be

discussed later), and is used to improve the surface strength of the titanium fan blades.

This will prevent cracks from forming. This step was particularly time-consuming as the

machine was only able to process one blade at a time with a cycle time of 20 minutes

per blade. After this step, the author brought the blades to the final station – the vibro-

polish station. The blades were loaded onto the polishing machine and submerged into a

tank of pink aluminium oxide media. The machine vibrated the blade, causing the

Aluminium Oxide to rub against and polish the surface. After the blades had been

polished, the author’s last task was to measure the surface roughness of the blades, to

ensure that they were compliant to Rolls-Royce standards. Once all 26 blades had

passed the checks, her assignment in the fan blade cell was considered complete.

3.2. Fitting cell The next cell that the author was attached to was one of the most important cells in

SAESL – the fitting cell. Unlike the fan blade cell, all subsequent cells that the author

was attached to were process cells that specialized in processes, not components.

Repairs in this cell are carried out manually by technicians, using simple hand tools like

drills, grinders and even penknives. As a result, this cell covers a very wide range of

Surface of Engine-run blade Surface of glass-peened blade Surface of vibro-polished blade


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repairs in SAESL, because the repairs are not limited by the capabilities of the machines

employed in other cells.

Figure 9 – the workflow for the repair of a composite fairing

The author spent a week at the fitting cell, repairing composite fairings. A fairing is a

light-weight structure used to cover oddly-shaped protrusions on the aircraft, making it

more streamlined and hence reducing drag. It is made of a carbon fibre sandwich, with a

honeycomb core in the middle, making it extremely lightweight. In the component sent

for repair, the carbon fibre had become delaminated from the honeycomb, and work was

required to bind it back. The author first drilled 1mm holes all over the carbon fibre in

the area that had become delaminated. These holes were used for forcing adhesive into

the sandwich, and the sandwich was then clamped together to allow the adhesive to cure.

After curing, as an additional measure, blank metal plates were screwed together on

both sides of the sandwich. The fairing was then considered successfully repaired.


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Although this was a complex process that took almost a day for each single fairing, the

author was able learn a lot, from wielding the tools, to making the metal blanks and

mixing the necessary products to make the adhesive. Through the process, the author

also learned about safety standards in the work place, as well as other aerospace

standard practices like tool box organization – tools are placed in toolboxes in

customized grooves, known as shadow boxes, which make accounting for the tools easy

after each repair, ensuring that no tools have been accidentally left on the component. In

her attachment to this cell, the author was able to understand and appreciate the menial

jobs that the technicians were required to carry out, and which helped her understand

the shop floor operations much better.

3.3. Shot peening cell The shot peening cell is new in SAESL, only set up in September 2009 by the repair

development department. Shot peening is a process used on metals that will increase

surface hardness. Countless small spherical particles (known as shots) are thrown at the

metal surface at a very high speed, deforming the molecules and creating residual

compressive stress on the surface. This internal stress will act against external tensile

forces to increase the strength of the metal, and will prevent crack propagation, as seen

in figure 10 below.

Figure 10 – fundamentals of shot-peening

Deformed molecules Crack being pushed together


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Rolls-Royce has stipulated the use of the shot peening treatment on many metal parts

deemed to undergo a lot of stress during engine run. Because shot peening is a very

complicated technology due to the randomness in the firing of the shots, it is a very

carefully controlled process by Rolls-Royce. The approval to carry out this process is

granted only to a select few companies worldwide, including SAESL, who have

demonstrated their shot-peening capability to Rolls-Royce.

In SAESL, shot-peening is a fully automatic process. A nozzle is affixed to the head of

a 6-axis robot, and the shots are fired from the nozzle. The speed and volume of the

shots being fired per second is controlled by the shot peening machine. The component

to be peened first has to be masked – using rubber plugs to cover and protect the areas

of the component not meant not be peened. Then, the part is mounted on to a rotating

turntable in the booth. For each type of repair of each part, a computer program has

been written for it, directing the movement of the nozzle (i.e. robot arm), the intensity

and volume of the shots being fired, and the rotation of the turntable. Once the part is

loaded into the machine, the doors are closed, and the machine is set to run

automatically.

The attachment to the cell for the author was relatively simple, as the process was

completely automated. However, through the attachment, the author learnt about the

properties of the different metals in a jet engine and the fundamental theory of shot

peening. Also, through maintaining the shot peening machine, the author learnt about

the mechanics of the machine, and how the shots are processed, both before, and after

being fired.


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3.4. Machining Machining is an age-old process used since the 18th century, and involves using a cutter

to remove material from a component to achieve a desired geometry. It is one of the

most important processes in any production or repair factory, and likewise in SAESL.

Like the shot peening cell, the cutting tool on the machine is also attached to a robot.

However, the machining robots only move in 3-axes (up, down, left, right, front and

back), and are manually operated.

Machining can be broadly divided into 4 categories:

• Turning: is where the cutting tool is stationary, and the work piece rotates.

• Milling: is where the work piece remains stationary and the cutter is a rotating,

multi-tooth cutter. The axis of rotation of the cutter is often perpendicular to the

work piece.

• Drilling: the creation of cylindrical holes using twist drill on a stationary work

piece.

• Grinding: a process used mainly for finishing touches on surfaces, removing

very small amounts of material.


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Figure 11– Types of machining: a) Turning; b) Milling; c) Drilling; d) Grinding

One of the most important steps in machining is the clocking of the reference datum.

Because the cutter only has 4 axes of motion, the position of the repair component is

very important. In drilling, it is important that the surface to be drilled is set

perpendicular to the cutting tool. Likewise, in turning, the component to be machined

must be placed directly at its centre of rotation. If it is slightly off-centre, the machine

will wind up cutting too deep into one side of surfaces, and not cutting the opposite side

at all. The clocking process is carried out using a pressure dial attached to the robot in

place of the cutting tool. When clocking the reference datum, the dial should read a

constant pressure from the spindle for the entire surface. If there are abnormalities in the

a) b)

c) d)


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readings, the repair part will then have to be re-positioned. After the part has been

positioned, the cutting tool is attached to the robot, and the operator will begin

machining it. The parameters to be controlled are the speed of rotation of the component

(for turning), the speed of rotation of the cutting tool (for drilling and milling), and the

position and movement of the cutting tool. After machining, the operator has to finish

off the machined surface by hand, using sandpaper to even out the texture of the metal.

Figure 12 - Clocking the reference datum before drilling

This attachment was particularly interesting for the author, as machining is a

fundamental industrial process. The author was able to identify the various cutting tools,

as well as recognize the purposes and surface finish created by each tool. The author

was also able to learn from the experienced technicians and operators the speed at which

the tool/work piece should be rotated to achieve a clean surface finish. The author now

understands the machining process much better, which is knowledge that will come in

useful both in the production and the overhaul industry.

Chapter Four – Repair Scheme Reviews

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4. Repair scheme reviews The author’s orientation to the shop floor was aimed to prepare her for her next task –

taking charge of SAESL’s scheme review system. SAESL is a Rolls-Royce MRO shop,

servicing only Rolls-Royce engines and parts. As such, all repairs carried out by SAESL

are governed by repair schemes planned by Rolls-Royce, known as Full Repair

Schemes (FRSs). FRSs are designed by Rolls-Royce engineers to dictate all repair

procedures, and are meant to cover any form of defect or damage that may occur to any

component of the engine when in use. Any damages not identified by the FRSs will be

considered irreparable, and the part will be scrapped. Being in charge of reviewing the

FRSs, the author’s responsibility was to constantly update SAESL’s own repair

capability database according to each FRS in the Rolls-Royce database. Rolls-Royce

constantly updates and creates new FRSs, and the author was required to ensure that

SAESL’s own database accurately reflected the company’s ability to carry out each

repair. The technicians at the Inspection Cell will then refer to the database to determine

if a certain repair can be carried out within the SAESL facility, or if it is necessary to

send the part to a sub-contractor who is able to carry out the repair. To document the

process, the author will use a case study of FRS K004 as attached in Appendix B, which

is a repair scheme for repairing cracks at the front flange bolt holes of the Combustion

Rear Inner Case (CRIC). In the subsequent paragraphs, the author will explain the

procedure of reviewing an FRS.

Figure 13 – Flowchart for the scheme review database

Rolls Royce

Full Repair Scheme

• Technicians in the inspection cell

• SAESL engineers

SAESL database

Author

Provides:

Reviewed by: Input to:

Accessed by:


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Figure 14 – The combustion rear inner case

FRSK004 dictates the repair of a CRIC, as shown in the figure above, whose bolt holes

have cracked during engine run. First, the cracks are dressed, i.e. enlarged, to create a

suitable profile for subsequent welding. This is to ensure that the weld filler is able to

enter the space of the small crack. After dressing, the crack is then filled with filler from

argon arc welding. Following the welding, the CRIC is sent for heat treatment to relieve

it of the thermal stresses occurred during welding, before being machined to the final

required dimension. To conduct a proper scheme review, there are several areas that

require attention.

4.1. Standard Equipment As found in section 2 of FRSK004, and in all FRSs, there exists a list of standard

equipment required to conduct the repair. This repair calls for argon arc welding

equipment, copper chills, degreasing equipment, drill bits, hand tools, heat treatment

equipment, inspection equipment, machining equipment, penetrant crack test equipment,

swab etch equipment, vapour blasting equipment, and finally vibration peen equipment.

It was the author’s responsibility to ensure that all equipments were available and

functional in SAESL, before carrying on with the repair. If there were to be certain


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equipment that were not available in-house, the author was then required to identify the

unavailable procedures, and make arrangements for the procedures to be sub-contracted

to a third party vendor to complete the repair. In order to carry out this step, it was

necessary for the author to have a firm knowledge of all equipments available in

SAESL, which took a few weeks, and many trips to each individual cells, to acquire.

4.2. Consumable Materials Consumable materials, otherwise known as OMat, are the substances and products used

up in the process of the repair. It is, although smaller in scale, as important as the repair

equipment, as a repair cannot be carried out without either. The author was required to

ensure that SAESL constantly maintained a stock of all OMats required for each repair.

If there were OMats which SAESL did not maintain a stock of, the author had to ensure

that there were either other equivalent OMats available, or bring the matter to the

attention of the Materials Planning department, who would then stock the missing OMat.

4.3. Equipment capabilities In the most important step of reviewing a repair scheme, the author had to assess the

capabilities and limitations of the equipment, and if it were capable of carrying out the

task. In the FRSK004 example, dressing and welding were manual repairs carried out

by technicians, and usually face no capability problems. However, repairs using

machines and other complex equipments face more constraints. In heat treatment, it is

important to note if SAESL’s furnace is large enough, and if it is able to reach the

specified temperatures. In machining, because most machines only move along 4-axes,

it is important to note if the surface areas that require machining are accessible by the

cutting tools on the machines. This is the most complex step of the review, and the


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author had to learn the capability of each individual machine, or seek the opinion of an

operator with such knowledge. It was through this exercise that the author was able to

learn much more about the functions and mechanic principles of the various machines.

After confirming all above criterion, the author was required to fill in necessary

paperwork in the SAESL database. The standard forms, filled out to FRSK004, are

attached in Appendix C. After filling out the forms and updating it into the SAESL

database, the review would be considered complete. Hence, in the future, if the

inspection technicians were to notice a defect on the CRIC that required a FRSK004

repair, they would be able to see, through the database, if SAESL was able to handle

this repair, or if it had to be sent to a sub-contractor. A summary of the scheme review

process is shown in the diagram.

Figure 15 – Flowchart of the scheme review process

Full Repair Scheme

Equipment

Yes

No Outhouse

Consumables

Yes

No Request to purchase

Equipment capability No Outhouse

Yes Develop solution to overcome equipment limits

D

A

T

A

B

A

S

E


24

Through her task of reviewing and updating more than two hundred FRSs, the author

had become more familiar with the administration style of Rolls-Royce. She also gained

much more knowledge about all shop floor operations in SAESL, as well as established

a strong rapport with the technicians, known commonly as “the hands on the ground”. It

was a meaningful task for the author, as she was not only able to contribute to the

company by updating its database, but also benefitted from the learning experience of

this task.

Chapter Five – The Front Combustion Liner Cell

25

5. The Front Combustion Liner cell No attachment to the Repair Development department would be complete without

taking up a development project. During the author’s attachment to the department, she

joined a team of two other colleagues, in the process of building a new repair cell, the

Front Combustion Liner (FCL) cell. The first in Singapore and second worldwide to

service Rolls-Royce FCLs, the new cell incorporates cutting edge technologies which

will be explained in subsequent sections. As the project is still under development,

much of the information is confidential, and cannot be discussed in detail.

5.1. The Front Combustion Liner An FCL is commonly known as a combustion chamber, and is the component in which

the combustion in a jet engine takes place. A cross section of the FCL is shown in the

figure below; while the combustor assembly is shown in figure 5 of section 2.3. The

FCL is a fairly complex component due to the extremely high temperatures and

velocities of the airflow involved, in excess of 2100˚C and 150m/s respectively.

Figure 16 – Cross section of a combustion chamber


26

As can be seen from the figure 16, only a small portion of the airflow enters the FCL

directly. The rounded section at the front of the FCL, known as a Head, acts as a

diffuser to slow down the airflow coming into the FCL. The remaining air either enters

the airflow through several holes all around the FCL, or only rejoins the air at the end of

the combustion process, to cool the airflow before it enters the turbine. Fuel is sprayed

through nozzles in the head to create a combustible air/fuel mix, before being ignited.

The lowered-velocity airflow, coupled with the recirculation of the air caused by the air

entering the FCL through holes in the wall, is then able to sustain a steady flame.

The walls of the FCL are lined with ceramic-coated tiles, known as liner tiles. These

tiles are designed to contain the heat of the flame, and its cooling technique is shown in

the figure below. Infinitely many cooling holes are drilled into the walls of the FCL, as

seen in Figure 17a). These holes allow the cool air running outside the FCL to transpire

into it. Then, as seen in b), the cool air impinges on the tile, before moving through the

gap between the tile and the wall, cooling it through convection. These tiles are

removable for easy maintenance and replacement. In carrying out repairs on the FCL,

the tiles are always removed before any work is to be done on it.

Figure 17 – Close-up of the FCL: a) Cooling holes b) Liner tiles

a) b)


27

5.2. GOM machine – Optical measuring technique In attempting to automate all processes in the FCL cell, SAESL imported a relatively

new technology of 3D optical measuring from German company GOM – their

Advanced Topometric Sensor (ATOS) system for the purpose of inspection. The central

projector on the ATOS unit projects a unique fringe pattern on the FCL, and the two

cameras mounted on either side of the projector is able to measure the 3-D coordinates

of the fringe pattern based on the triangulation principle as illustrated in the figure

below.

Figure 18 – The GOM scanning unit and the triangulation principle

Through measuring the coordinates of the fringe patterns projected onto the FCL

surface, ATOS generates a cloud of 3D coordinates that map out its surface. The GOM

software on the computer then transforms the coordinates into an editable mesh. After

making necessary adjustments to the mesh (removing anomalous points and redefining

complex edges), the solid surface of the FCL is then generated. A semi-generated

Projector

Cameras

α β l

d?


28

(software is not completely set up) FCL is shown in the figure below, and in Appendix

D.

Figure 19 – The Front Combustion Liner in scan (left) and in 3-D model (right)

As mentioned previously, the GOM ATOS system is used for inspection. Inspection is

done by comparing the solid surface of the live FCL to pre-existing Computer-Aided

Design (CAD) data, created by the author on the SolidWorks program. The Solidworks

model, shown above and in Appendix D, is created from technical drawings from Rolls

Royce, and represents the ideal shape and geometry of the FCL. The GOM software is

then able to calculate and display the surface deviation between both models (example

shown on following page), and hence highlight the areas of deformation on the live FCL.

Figure 20 – Inspection data of the FCL


29

Although the setup of the GOM inspection is still a work in progress, the advantages are

clear. By automating the process, not only does it save time, inspection is also less

subject to human error and oversight – one of the largest problems with visual

inspection.

5.3. DMG – Automated Machining The other new technology employed in the FCL cell is the DMG (Deckel Maho

Glidemeister, a German machining company) machine, used to carry out adaptive

machining. Adaptive machining is an up-and-coming technology in the aerospace

industry[3], and SAESL is one of the first MRO firms in Singapore to employ it in its

operations. In the subsequent paragraphs, the author will explain the principle of

adaptive machining. As it is still under development, information regarding its purpose

in the FCL cell is confidential to SAESL and will not be discussed in detail.

The adaptive DMG machine begins by probing the surface of the component, in this

case, the FCL. This is to determine the exact position of the FCL, and hence set the

reference datum of the cutting tool. This saves time as there is no need to clock and

adjust the position of the as opposed to conventional machining (section 3.4).

Figure 21 – The probe of the adaptive machine


30

The DMG machine then uses the same probing tool to probe the surface that requires

machining, for example, a welded area that needs to have its geometry and dimensions

restored. As welded surfaces are often uneven, the probe traces the surface of the weld,

and is able to effectively communicate the path that the cutting tool should take when

machining the weld. This helps to avoid over/under-machining, which is a common

problem for conventional machining when faced with uneven surfaces. With intelligent

adaptive machining, the cutting tool knows the exact topography of the surface, and is

able to adjust accordingly to give an even thickness on the finished product.

Figure 22 – Probing an uneven surface before machining [3]

Another application of the adaptive DMG machine that is particularly relevant to the

aerospace industry is its ability to machine components that have been distorted out of

their original shape. As jet engines run at extremely high temperatures, many

components, especially the FCL, that come in for repair are seldom still in their original

shape due to heat distortion. In such cases, the GOM technology will be able to detect

the deviation of the part’s geometry, and coupled with the surface probing by the

adaptive machine, a customized toolpath can be generated for the machining of the

distorted part that would otherwise have been a slow and manual process.


31

In helping to set up the two state-of-the-art machines in the FCL cell, the author has

gained much knowledge. Not only did the task provide her with a glimpse into the

future of the MRO industry in optical scans and adaptive machining, it also taught her

the fundamentals of what it meant to be an engineer – to identify new technologies,

recognize their potential to suit your needs and adapt it accordingly, while keeping an

agile mind to deal with all the problems that crop up along the way.

5.4. Planning the repair matrix The author’s other task with the FCL cell was more administrative – planning what is

known as a repair matrix. There are several repair schemes that govern the repairs of an

FCL, and any FCL that comes into SAESL would possibly require none, one, more, or

all of the repairs. The repair matrix, as attached and shown in Appendix E, combines all

the repair schemes of the FCL, or any other component in question, and groups similar

processes, such as cleaning, or machining together. The order of the individual repair

schemes cannot be jumbled (i.e. if the repair scheme calls for welding before machining,

the FCL must first be welded before being machines). Care must also be taken when

fitting the repairs together, as certain repair processes may interfere with each other, and

cannot be simply combined. A simple example is shown below:

Component X Repair 123 Repair 456 Cleaning x x Inspection x x Water jet stripping x Plasma coating x Welding x Machining x x

Figure 23 – A sample repair matrix


32

By planning such a matrix, it ensures that all FCL components that arrive in SAESL for

repair is able to have any combination of repairs carried out on it in a very efficient

manner, as the repairs are able to run side-by-side, instead of first completing repair 123,

before starting on repair 456. Such efficient systems allow SAESL’s manufacturing

processes to be leaner, hence contributing to SAESL’s overall productivity, and market

competitiveness.

Chapter Six – Personal Reflections and Conclusion

33

6. Personal Reflections and Conclusion

6.1. Personal Reflections The 22 weeks I spent at SAESL has been an incredible learning journey, and will

certainly be one that I carry with me through my working life. It has provided me with a

wonderful introduction not only to the career and daily life of a professional aerospace

engineer, but also to the fundamental operations of any engineering firm.

When my mentor, Adrian, arranged for me to be attached to the various repair cells, his

purpose was for me to not only gain hands-on experience with the engine components,

but also to have a greater understanding of the technicians and the work that they do. He

believes that in order to know a process, person or machine well, one has to get his hands

dirty, to know their problems, to respect, eat and sweat with them. This understanding is

important for an engineer, as engineers are the “brains” in the office, planning the repairs

and procedures for the technicians, commonly known as the “hands”, to follow. Without

a good understanding of the technicians’ capabilities, engineers will face problems in

their planning processes. Through my attachment at the repair cells, firstly, I was grateful

for the opportunity to see and handle the engine components that I had previously only

read about and seen pictures of in textbooks. This greatly enhanced my understanding of

the jet engine, through my understanding of its individual components. However, more

importantly, I was able to build up a good rapport with the technicians in the various

cells, as they imparted their years of experience and wisdom to me. In helping to carry

out repairs, I was also able to fulfill Adrian’s target for me – to know the capabilities and

the limitations of the technicians and the tools they access, so as to enhance my own


34

understanding of the shop floor, and hence improve my planning capabilities as an

engineer.

In my second task at SAESL, taking charge of the scheme review database, although

seen as a mundane task, was actually very interesting for the author. Having made friends

with the technicians, this task became relatively simple, as I was able to seek their

opinions on SAESL’s or even their own repair cell’s capability on the various repairs.

This task exposed me to many engine parts that I did not have a chance to handle while I

was in the repair cells, as I had only worked on a few components. In addition, I was also

introduced to other repair and process cells outside of the four cells I was attached to.

These included the cleaning line, the plasma cell, and several other cells that I was

formerly unfamiliar with. This enabled me to learn more about the various cells not just

in SAESL, but in any standard jet engine Maintenance, Repair and Overhaul shop. All in

all, I felt that this task really familiarized me with the standard operations of an MRO, as

most jet engine companies, such as General Electric and Pratt and Whitney, adopt similar

working styles, building their MROs around repair schemes dictated by the engine

makers.

Of course, the most enriching learning experience was my most important, and indeed,

most interesting task – the setting up of the FCL cell. Setting up this cell was quite a

roller coaster, and I regret that it was not able to be completed before the end of my

attachment. This task taught me several key skills of becoming an engineer. The main

machines, the GOM and the DMG, as explained in Chapter 5, were the brainchild of my

colleague, Alex, who noticed these up-and-coming technologies, and saw their potential

to meet his needs in the FCL cell. However, the setting up of these machines proved to


35

be no simple task. A new problem arose from the machines almost every day in the

starting stages, and through learning to identify and overcome these problems on a daily

basis, I learnt the importance of being a quick and critical thinker as an engineer.

Machines, no matter how developed they become, will never be perfect substitutes for

human labour. However, in this day and age, machines are extremely vital in any

engineering process and hence, all good engineers must learn to work with machines, and

be able to deal with any problems that the machines may throw at you. The second thing

that I learnt was the ability and willingness to pick up any new skills that may be

required of you in your workplace. When I first entered SAESL, I had little knowledge

about Solidworks, or any Computer Aided Design software for that matter. However,

when CAD models were required for the GOM machine in the FCL cell, I had to learn it

quickly to meet this need. I borrowed books from libraries, sought help from online

forums, and was able to pick up the skill in time to draw the rather complicated FCL

model, as is shown in Appendix D. I learnt that we may not always have the necessary

skills, but it is important to be willing to learn in order to maximize your own

productivity for the company. Another learning journey was the background work that

went on for the setting up of the FCL cell. As engineers, it is easy to assume that our

responsibilities are mainly to handle the machines. However, that is not true. An engineer

that handles a project will have to liaise closely with the management for their support,

with financial managers to ensure that the project is operating within budget, with safety

officers to ensure that safety standards are being met, etc. A project is never a one man

show, and engineers must also display communication prowess in seeing a project to its

successful completion. This task has equipped me with many critical professional skills

that can be applied to my career, not only in engineering, but in other industries as well.


36

Along the way, I have also taken up several small projects, of which there are too many

to document in this report. For example, I have written computer programs to automate

the processing and updating of information for databases in SAESL. These programs will

greatly simplify processing the database for my colleagues in the future. Most

importantly, I have learnt that a willing attitude is very important in the workplace. One

must never be too calculative about his/her own workload, must be willing to learn the

things he/she does not know, and must always help your colleagues when possible.

6.2. Conclusion In conclusion, I would like to thank all my colleagues in the Engineering Department,

who went out of their way to assist me in my inexperience, and who made my initiation

to the working life very enjoyable. Their warm-heartedness was very much appreciated

to a fresh student who had not worked in the capacity of an engineer before, and I

sincerely hope to have the chance to be their colleague once again.

I hope that I have been of good service to SAESL, and that the projects and tasks that I

have undertaken will be useful to their operations. SAESL is indeed a company at the

forefront of the MRO industry, and I am honoured to have completed my Industrial

Attachment here.

The lessons and skills that I have picked up in SAESL will accompany me no matter

where I go, and I now await my return to school in September 2010, where I am sure my

increased knowledge of the jet engine, and the aerospace industry, will be very useful to

my academic pursuit.

Chapter Seven - References

References

[1] Singapore Aero Engine Services Limited. (n.d.) Our Facility Retrieved 21 May 2010, from http://www.saesl.com.sg/index.html

[2] Rolls Royce. (2005). The Jet Engine. United Kingdom: St Ives Westerham Ltd.

[3] Peter Dickin, November 2008. The Adaptive Approach. Control Engineering Asia

http://www.saesl.com.sg/index.html

Appendix

Appendix A – Organizational Chart of SAESL

CEO

Gary Nutter

Manager Finance & AdminWoo Lai Kuen

ManagerEngineering, HS&EChan Swee Heng

Manager Quality & C I

Tay Hang Chua

ManagerProduction

Leck Tea Kiang

Manager Cust Business Lawton Green

Snr Mgt Asst - Elsie Chan Mgt Asst - Stephanie Sim

Senior Mgt AccAudrey Pang

Head Fin A/gNicholas Cheong

Head Engrg(Overhaul Support) Gan Chin Yee

Head HS&EJohnny Cheng

Head Gen Repairs IYap Joo Ann

Head B3Yeo LP, Choy WP,

Leonard

Head B0Hamzah, Greg,

Chang

HeadTham JL

Manager Component Repair & Material

Tan Wai Meng

HeadLog & Warehousing

Jeffrey Ng

Head Material PlanningRavind

Finance Exec Finance Asst

Accountant A/C ExecsA/C Assts

HR Execs Snr/Tech Svc EngrsAsst Tech Svc Engrs

Procurement Execs

Material PlannersKitting Assts

Inspectors, Trainers,Technicians &Trainees

Inspectors, Trainers, Technicians,

Operators & Trainees

Cust Biz Exec (Head) David Su

Cust Biz Execs

Facilities Maint

� Finance & A/Cs Function� Business Plan deviation

monitoring� Liason with auditors� Prepare Company Finance

Manual� Provide Financial

performance� Company Secretary� Cash Management� Asset� Cashier� Credit Control� Legals� Facilities Maintenance

� Product Engineering� Workscope Requirement� SB Control / AD� Technical Library � Process Sheets� Safety� Workscope � T.V. Evaluations � HS&E

� Engine Receipt, Strip, Build,Prepare for Test, DespatchPrep & mvmt

� Module; Strip & Build,

� Clean, NDT,� Maintenance of Equipment

� Material Planning� Procurement� Control of Vendors� Shipping and receipt of

Goods� Warehousing� Kitting

� Head of Biz Process� Marketing� Sales� Bio Evaluation� Customer Comm & Sppt� Margin Protection� Contract Maintenance� HAESL, Head of Marketing

Liason� Credit Control

SAESL STRUCTURE - Key Roles / Responsibilties

ManagerPlanning & IT

Khoo Kee Swee

4 Layers StructureTo Man an Integrated Business and Production Processes

ManagerHuman ResourcesChristina Lee

Cust Biz Coordinators

Head HRMLynn Lim

Head, CompressorBlade

Sean Ho

Head Engrg(Repair & Support)

Chris Chu

Engineering SpecialistsSnr/Tech Svc EngrsAsst Tech Svc EngrsTechnical Coordinator

Head ProcurementAndy Goh

Material PlannersKitting Assts

Head Material Planning II Gary Goh

Head Plasma CoatingNg Boon Wee

HS&E Exec

Head Planning & IT Iris Tan

Prod Planners

IT Executives

� ContractManagement for IToutsourcing

� Master Planner� Production Planning� Production Status

� Staff Recruitment� Compensation & Benefits Mgt, Payroll� Learning & Devmt� Employee Relations� Grievance Procedure

� Direct access forQuality relatedmatters

� ISO 9000/ 14000� QA Admin & Audit� Technical Records� FAA, CAAS, JAA

Liason� Continuous

Improvement� Process Compliance

� General Repairs� Plasma Spray� Fan Blade Cell� Compressor Blade Cell� Lab Dev� Process Improvements

Black Belt CatherineAdrian

Trainee Black Belt Siew Tin Head NDT/ Cleaning

Oh Inn Chiam

Component Exec

PrincipalTechnologistKoh Li Teck

Updated as at 19 May 2009


Inspectors, Trainers,Technicians,


Equip Maint Tech

Head Sentencing Ng Kwee Liang


Head Gen Repairs IIRandy Yap





Head QualityGanesh

Quality Engineer Training & Dev Engineer

Head Quality Ku Eng Chuan

Snr/Quality Engineers Asst Quality EngineerTech Rec Officers

Head BET1 (Test Cell & E&I) Sean BooInspectors, Trainers,

Technicians &Trainees

Head Gen Repairs III Lewis Foo



LabTechnicians &Operators

HR Exec

Head HRD Ferry Falco

Head NDT(Standards)Hendrich Lim

Compressor BladeInspectors, Trainers,

Technicians,Operators & Trainees

Fan BladeInspectors, Trainers,

Operators & TraineesTechnicians,

Log Execs & Log AsstsLogistics

Store InspectorsWarehouse Assts

Warehousing

Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix

Appendix D – SolidWorks Model of the Trent 500 Front Combustion Liner

Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Appendix


Report2

Documents

repair development department

new repair cell

repair capabilities

author mr alex ong

attachment office

various repair cells

author mr koh li teck

engineering company